Synergistic effect of Trichoderma-derived antifungal metabolites and cell wall degrading enzymes on enhanced biocontrol of Fusarium oxysporum f. sp. cucumerinum

Abstract

Cucumber (Cucumis sativus L.) is an important vegetable crop grown worldwide. However, its productivity is largely suppressed the phytopathogen Fusarium oxysporum f. sp. cucumerinum (FOC). We screened 100 isolates of Trichoderma as potential biocontrol agents against FOC. Both in vitro and in vivo methods were used, followed by the analysis of synergistic effect of cell wall degrading enzymes (CWDEs) and its secondary metabolites. In addition, molecular target of growth regulating protein of FOC (Snt2, a BAH/PHD containing transcription factor) was also studied. Of the 100 isolates of Trichoderma, 10 isolates with more than 85% inhibition rate were selected for in vivo antagonism in greenhouse experiment. Trichoderma asperellum strain CCTCC-RW0014 was found to have good biocontrol potential with high disease reduction of 71.67%. The RT-qPCR analysis revealed that the ITS copies of T. asperellum CCTCC-RW0014 were significantly higher in the cucumber roots treated with T. asperellum CCTCC-RW0014. Whereas the ITS copies of FOC declined in plants root in the presence of T. asperellum CCTCC-RW0014 and FOC. T. asperellum CCTCC-RW0014 showed high hydrolytic activity of chitin (87.5±3.21%), gelatin (84.8±2.56%), carboxymethyl cellulose (52.9±1.23%) and pachyman (60.5±2.32%). The crude enzymes; namely chitinase, cellulase, protease, and β (1–3) glucanase; were optimally active at 40°C and pH 5.0, 30°C and pH 6.0, 40°C and pH 7, and 40°C and pH 6.0 respectively. The secondary metabolites of Trichoderma extracts were determined by GC–MS and further studied for the molecular docking against target protein Snt2. Among the tested compounds, 1, 6-diphenylhexane-1,3,4,6-tetrone showed the highest C dock energy (−27.567kacl/mol) against the target protein and this may down regulate the expression of protein Snt2. The present work concluded that T. asperellum CCTCC-RW0014 was the highly potential strain to control the FOC, providing scope for a further study on the mechanism of interaction between Trichoderma derived compounds and host plants.